简单深度优先搜索

#include <iostream>

using namespace std;
#define MAX_SIZE 20

using namespace std;

static int x = [](){std::ios::sync_with_stdio(false);cin.tie(0);return 0;}();
typedef struct A{
    int adj;
    int *ptr;
}Val[MAX_SIZE][MAX_SIZE];

struct Graph{
    int Vertex[MAX_SIZE];
    Val val;
    int vertex, arc;
};

int FindVertex(Graph *G, int v){//根据顶点数组判断顶点在二维数组中的位置
    for(int i = 0; i < G->vertex; ++i){
        if(G->Vertex[i] == v){
            return i;
        }
    }
    return -1;
}

void CreatGraph(Graph *G){//创建无向图
    cout << "Please input the number of vertex and arc:" << endl;
    cin >> G->vertex >> G->arc;
    cout << "Please input the data of vertex:" << endl;
    for(int i = 0; i < G->vertex; ++i)
        cin >> G->Vertex[i];
    for(int i = 0; i < G->vertex; ++i){
        for(int j = 0; j < G->arc; ++j){
            G->val[i][j].adj = 0;
            G->val[i][j].ptr = nullptr; 
        }
    } 
    cout << "Please input the relation of vertex and arc:" << endl;
    for(int i = 0; i < G->arc; ++i){
        int v, a;
        cin >> v >> a;
        int m = FindVertex(G, v);
        int n = FindVertex(G, a);
        if(m == -1 || n == -1){
            cout << "No!!!";
            break;
        }
        G->val[m][n].adj = 1;
        G->val[n][m].adj = 1;
    }
}

int Visited[MAX_SIZE];//记录顶点是否被访问过

int FindFirst(Graph *G, int v){//寻找顶点周围有边的顶点
    for(int i = 0; i < G->vertex; ++i){
        if(G->val[v][i].adj)
            return i;
    }
    return -1;
}

int NextVertex(Graph *G, int v, int w){//从下一个位置寻找，顶点周围有边的顶点
    for(int i = w + 1; i < G->vertex; ++i ){
        if(G->val[v][i].adj)
            return i;
    }
    return -1;
}

void PrintV(Graph *G, int v){
    cout << G->Vertex[v] << " ";
}

void DFS(Graph *G, int v){
    Visited[v] = true;//准备访问该顶点
    PrintV(G, v);//访问顶点
    for(int i = FindFirst(G, v); i >= 0; i = NextVertex(G, v, i)){
        if(!Visited[i]){//如果该顶点未被访问，则继续搜索
            DFS(G, i);
        }
    }
}

void DFSTr(Graph *G){
    for(int i = 0; i < G->vertex; ++i){
        Visited[i] = false;//设置全部顶点未访问
    }
    for(int i = 0; i < G->vertex; ++i){
        if(!Visited[i]){
            DFS(G, i);
        }
    }
}

int main()
{
    Graph *G = new Graph[sizeof(Graph)];
    CreatGraph(G);
    DFSTr(G);
    
    return 0;
}